Two units of whole blood transfusion typically raise hemoglobin by approximately

• A. 1 g/dL
• B. 2 g/dL
• C. 3 g/dL
• D. 4 g/dL

Answer: (B)

The main idea is that the effect of a transfused unit on hemoglobin is roughly additive. In an average adult, each unit of red cell-containing blood tends to raise the hemoglobin by about 1 g/dL. So giving two units adds up to roughly a 2 g/dL increase in Hb, reflecting the added red cell mass and its oxygen-carrying capacity.

Keep in mind this is a guideline rather than a precise rule. The actual rise can be influenced by the patient’s blood volume and turnover, ongoing blood loss, fluid resuscitation (which dilutes Hb), and the quality of the red cells in the product. That’s why the expected increase is approximate rather than exact.